Saving Hubble: a famous space telescope gets an out-of-this-world tune-up

Science World, Feb 18, 2008 by Jennifer Moser

[ILLUSTRATION OMITTED]

As the Hubble Space Telescope's 18th birthday approaches, officials at the National Aeronautics and Space Administration (NASA) are planning to send astronauts to visit it. No, the reunion won't be for a birthday party: Astronauts will blast into space to give Hubble a much-needed tune-up while it orbits Earth. The astronauts will repair and upgrade the telescope so it can continue to wow people as it has for nearly two decades with never-before-seen images of the universe.

HUBBLE'S BIG FINDS

Hubble orbits nearly 567 kilometers (352 miles) above Earth's surface--beyond the planet's atmosphere. Because light traveling from stars, planets, and other space objects doesn't have to pass through this protective layer of gases before reaching the telescope, Hubble's images are clearer than any images ever taken from ground-based telescopes.

Since its launch on April 24, 1990, Hubble has taken roughly 500,000 pictures. It has made approximately 800,000 total observations, including some that aren't pictures, says Zolt Levay, an image-processing specialist at the Space Telescope Science Institute in Baltimore.

Hubble's observations have helped astronomers make important discoveries about the universe. For instance, scientists have used data from Hubble to determine that the universe is 13.7 billion years old. They also discovered that the expansion of the universe is speeding up, and this faster and faster expansion is caused by a mysterious substance called dark energy. Dark energy is the source of a force that is opposite to gravity, making things travel apart from one another. Scientists still do not know much about dark energy.

PLEASE HELP HUBBLE

Hubble's jaw-dropping pictures of the universe also have excited the general public about outer space. About two million people per month visit http://Hubblesite.org, run by the Space Telescope Science Institute, to view Hubble images.

But the space telescope wasn't designed to last forever. In 2004, NASA made the decision to stop servicing Hubble. After the space shuttle Columbia suffered a fatal disaster in 2003, NASA decided that service missions would be too dangerous. Due to failing equipment, this decision would have meant that Hubble would stop working around 2010.

When NASA broke the news to the public, many people were outraged and disappointed at the thought of losing the telescope. "We were receiving letters from children who were prepared to donate their lunch money to save the Hubble," says Mario Livio, an astrophysicist at the Space Telescope Science Institute. Once NASA officials determined that maintenance to the telescope could be done safely, they decided to extend Hubble's lifetime.

SERVICE MISSION

If all goes as planned, on August 7 astronauts will depart for Hubble for the first time in six years. During the servicing mission, space-walking astronauts will install new batteries and new gyroscopes (devices that help direct the telescope). This should keep Hubble operating until 2013.

Astronauts plan to repair two scientific instruments on Hubble that have stopped working. In addition, they will outfit the telescope with a powerful new camera and a new spectrograph that can determine the temperature, composition, and speed of a variety of astronomical objects.

The astronauts also will begin preparing Hubble for its eventual end. Hubble orbits relatively close to Earth, so without intervention, the friction from Earth's atmosphere would cause the telescope to slow down and fall to Earth sometime after 2023, says Mike Weiss, Hubble's deputy program manager at NASA. Although much of Hubble would burn up in the atmosphere during its descent, some parts might survive. If they were to land in a populated area of the planet, they potentially could kill people. So astronauts will fit Hubble with a capture device.

Years from now, the capture device will help a NASA vehicle guide the 11,113-kilogram (24,500-pound) telescope safely to its destiny. The vehicle might guide Hubble back to Earth, landing it in the ocean so it can't harm people, or it might direct the telescope far enough into space that Earth's gravity would never be strong enough to pull it back.

NEXT-GENERATION TELESCOPE

Since Hubble won't last forever, scientists are already building the next telescope that will show us even more of the universe. The James Webb Space Telescope will be much larger than Hubble and will be able to see light from objects that are farther away than anything Hubble has ever imaged.

Because it can take billions of years for light to travel from distant galaxies to Earth and to Hubble, the images that space telescopes see actually show what occurred a long time ago. "To look out into space is to look back in time," says Fritz Benedict, an astronomer at the University of Texas, who works with Hubble. The James Webb, which scientists hope to launch in 2013, will be able to see the very first galaxies, back to the beginning of time, says Weiss.

nuts & bolts

HOW HUBBLE WORKS